CN107186911B

CN107186911B - Resin pelletizer apparatus and cavitation monitoring method

Info

Publication number: CN107186911B
Application number: CN201710151038.2A
Authority: CN
Inventors: 田伏谅; 高桥英二; 真锅知多佳; 荒木要; 岩崎伸; 宫本树
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2016-03-14
Filing date: 2017-03-14
Publication date: 2020-10-16
Anticipated expiration: 2037-03-14
Also published as: JP6639013B2; CN107186911A; JP2017164920A; DE102017104995B4; DE102017104995A1; US10160153B2; US20170259484A1

Abstract

Provided is a resin pelletizer device capable of monitoring cavitation. A resin pelletizer device (100) is provided with: a die (6) having a die surface (61) provided with a die hole (63); a rotary blade (21) which rotates on the die surface (61) in water to cut the resin extruded from the die hole (63) into pellets in water; a sensor (150) that detects an elastic wave generated by the rotating blade (21) rotating on the die surface (61); a determination unit (121) monitors the output value of the sensor (150), and determines that cavitation has occurred when the output value of the sensor (150) becomes smaller than a preset threshold value.

Description

Resin pelletizer apparatus and cavitation monitoring method

Technical Field

The present invention relates to a technique for molding a resin into pellets.

Background

The resin pelletizer device is a device for cutting a molten resin in a strip form (rope form) extruded from a die orifice into water by using a rotary blade rotating at a high speed on a die surface provided with the die orifice, and molding the resin into pellets.

A gap is provided between the die face and the rotary blade. If the gap becomes large, cutting failure of the molten resin occurs. The cutting failure is, for example, a case where particles having a beard-like portion or a plurality of particles connected in a chain form occur.

As a technique capable of monitoring the gap, a dicing failure detection method has been proposed, which includes: setting a reference position by abutting a cutter blade against the die surface and measuring the position of the cutter blade at the reference position setting timing; measuring the position of the cutter blade when the cutter blade is rotated to cut off the molten resin, and setting the measured position as the current position; and a step of reporting a warning of a cutting failure when the difference between the current position and the reference position is larger than a predetermined clearance setting (for example, see patent document 1).

Patent document 1: japanese patent laid-open No. 2001 and 38676.

The resin pelletizer device cuts the molten resin by rotating a rotary blade at a high speed on a die surface in water, but cavitation may occur at this time. Cavitation is a physical phenomenon in which generation and extinction of bubbles occur in a short time due to a pressure difference in a flow of liquid. The present inventors found that poor cutting occurs due to cavitation. A technique capable of monitoring cavitation during operation of a resin pelletizer device is desired.

Disclosure of Invention

The invention aims to provide a resin pelletizer device capable of monitoring cavitation and a cavitation monitoring method.

A resin pelletizer device according to claim 1 of the present invention includes: the die is provided with a die surface provided with a die hole; a rotary blade which rotates on the die surface in water to cut the resin extruded from the die hole into pellets in the water; a sensor for detecting an elastic wave generated by the rotary blade rotating on the die surface; and a determination unit that monitors the output value of the sensor and determines that cavitation has occurred when the output value of the sensor becomes smaller than a preset threshold value.

The elastic wave (e.g., ultrasonic wave, vibration) generated when the rotating blade rotates on the die surface is detected by the sensor. The present inventors have found that, although the output value of the sensor increases as the rotation speed of the rotary blade increases, the output value of the sensor decreases if cavitation occurs. This is considered to be because the rotating blade is shaken by the occurrence of cavitation.

Cavitation causes cutting defects. Therefore, the determination unit monitors the output value of the sensor, and determines that cavitation has occurred when the output value of the sensor becomes smaller than a preset threshold value. Therefore, according to the resin pelletizer apparatus according to claim 1 of the present invention, the cavitation can be monitored.

In the above configuration, the controller may further include a notification unit that notifies occurrence of the cavitation when the determination unit determines that the cavitation has occurred.

This structure reports the occurrence of cavitation when it is determined that cavitation has occurred. Therefore, the operator of the resin pelletizer device can take measures necessary for the occurrence of cavitation (for example, measures to reduce the number of rotations of the rotary blade, measures to stop the operation of the resin pelletizer device).

In the above configuration, the resin pelletizer apparatus further includes a stop control unit that stops the operation of the resin pelletizer apparatus when the determination unit determines that the cavitation has occurred.

This structure automatically stops the operation of the resin pelletizer when it is determined that cavitation has occurred.

In the above configuration, the determination unit compares a 1 st threshold value and a 2 nd threshold value smaller than the 1 st threshold value with the output value of the sensor, as the threshold values; further provided with: a reporting unit configured to report that the cavitation has occurred when the determination unit determines that the output value of the sensor is smaller than the 1 st threshold and equal to or greater than the 2 nd threshold; and a stop control unit configured to stop the operation of the resin pelletizer when the determination unit determines that the output value of the sensor is smaller than the 2 nd threshold value.

When cavitation occurs, the output value of the sensor decreases as the rotational speed of the rotary blade increases. The shaking of the rotary blade is considered to be a cause thereof. If the wobbling of the rotary blade becomes large, the degree of cutting failure is further deteriorated. For example, a plurality of particles connected in a chain shape is produced. This causes the particles to clog in the interior of the resin pelletizer device.

Therefore, when the determination unit determines that the output value of the sensor is smaller than the 1 st threshold and equal to or greater than the 2 nd threshold, it is considered that no large problem (for example, particles having a beard-like portion due to cutting failure) occurs in the resin pelletizer device, and the notification unit notifies the occurrence of cavitation. On the other hand, when the determination unit determines that the output value of the sensor is smaller than the 2 nd threshold value, it is considered that a large problem (a plurality of particles connected in a chain shape, for example, is generated due to a cutting failure) occurs in the resin pelletizer device, and the stop control unit automatically stops the operation of the resin pelletizer device.

In the above configuration, the apparatus further includes: a storage unit that stores in advance an upper limit value of the rotational speed of the rotary blade at which the cavitation does not occur; and a rotation control unit that controls the rotation speed of the rotary blade to a value not exceeding the upper limit value.

According to this structure, occurrence of cavitation can be prevented.

A cavitation monitoring method according to claim 2 of the present invention is a method of monitoring cavitation generated in a resin pelletizer apparatus including a die having a die surface with a die hole and a rotary blade rotating in water on the die surface to cut resin extruded from the die hole into pellets in the water, the method including: a step 1 of detecting an elastic wave generated by the rotating blade rotating on the die surface; and a 2 nd step of monitoring the magnitude of the elastic wave detected in the 1 st step, and determining that cavitation has occurred when the magnitude of the elastic wave becomes smaller than a predetermined threshold value.

The cavitation monitoring method according to claim 2 of the present invention defines the resin pelletizer apparatus according to claim 1 of the present invention from a method point of view, and has the same operational effects as the resin pelletizer apparatus according to claim 1 of the present invention.

According to the present invention, it is possible to monitor cavitation occurring in the resin pelletizer device.

Drawings

Fig. 1 is a block diagram showing a configuration of a resin pelletizer apparatus according to the present embodiment.

Fig. 2 is a sectional view of the main body of the resin pelletizer device.

FIG. 3 is a plan view of FIG. 2 viewed from the direction IIIa-IIIb.

FIG. 4 is a plan view of FIG. 2 viewed from the direction IVa-IVb.

FIG. 5 is a plan view of FIG. 2 as viewed from the direction of Va-Vb.

Fig. 6 is an explanatory diagram for explaining cavitation generated during operation of the resin pelletizer device.

Fig. 7 is a graph showing a relationship between the rotation speed of the rotary blade and the output value of the sensor.

Fig. 8 is a flowchart illustrating control of the resin pelletizer using the 1 st threshold value and the 2 nd threshold value.

Detailed Description

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a block diagram showing a configuration of a resin pelletizer apparatus 100 according to the present embodiment. The resin pelletizer device 100 includes a resin pelletizer device main body 110, a control unit 120, an operation panel 130, a notification unit 140, and a sensor 150.

The resin pelletizer apparatus main body 110 will be explained. Fig. 2 is a sectional view of the resin pelletizer apparatus main body 110. FIG. 3 is a plan view of FIG. 2 viewed from the direction IIIa-IIIb. FIG. 4 is a plan view of FIG. 2 viewed from the direction IVa-IVb. FIG. 5 is a plan view of FIG. 2 as viewed from the direction of Va-Vb.

Referring to fig. 2, the resin pelletizer apparatus main body 110 includes a chamber 1, a rotary head 2, a rotary shaft 3, a bearing 4, a motor 5, and a die 6. The rotary head 2 is disposed in the chamber 1 at an inner portion 11 thereof. The rotary head 2 is fixed to one end of the rotary shaft 3. A through hole is formed in a wall surface 13 of the chamber 1 intersecting the rotary shaft 3, and the bearing 4 is fitted therein. The bearing 4 supports the rotary shaft 3. The other end of the rotating shaft 3 extends out of the chamber 1 and is connected to a motor 5. If the motor 5 rotates, the rotary shaft 3 rotates, whereby the spin head 2 rotates.

Referring to fig. 2 and 3, the rotary head 2 includes four rotary blades 21 and a fixing portion 23 for fixing each rotary blade 21. The fixing portion 23 has a truncated cone shape, and the rotating shaft 3 is fixed to one end surface of the fixing portion 23. On the other end surface (the bottom surface 231 of the truncated cone) of the fixing portion 23, four rotary blades 21 are arranged at intervals of 90 degrees. The case where the number of the rotary blades 21 is four is exemplified, but the number of the rotary blades 21 is not limited to four.

The rotary blade 21 has a substantially rectangular shape, and the longer direction of the rotary blade 21 is directed in the radial direction of the other end surface (the bottom surface 231 of the truncated cone) of the fixed portion 23. One end 211 of the rotary blade 21 is fixed to an edge of the other end surface (the bottom surface 231 of the truncated cone) of the fixed portion 23, and the rotary blade 21 rotates outside the other end surface (the bottom surface 231 of the truncated cone) of the fixed portion 23.

A through hole is formed in the wall surface 15 of the chamber 1 facing the other end surface (the bottom surface 231 of the truncated cone) of the fixing portion 23. The through hole is closed by the die 6.

Referring to fig. 2 and 4, the die 6 has a die face 61 disposed in the interior 11 of the chamber 1. The die surface 61 has a disk-like shape, and a plurality of die holes 63 are formed in the die surface 61 at equal intervals in a ring shape. The die hole 63 penetrates the die 6. Referring to fig. 2 and 5, a die hole 63 is opened in a path in which the rotary blade 21 rotates, and a molten resin extruded by an extruder (not shown) passes through the die hole 63 and is extruded from the die hole 63, and is cut by the rotary blade 21 on the die surface 61. Thereby, the molten resin is formed into pellets.

Referring to fig. 2, during operation of the resin pelletizer apparatus 100, the interior 11 of the chamber 1 is filled with water, and the rotary head 2, the die face 61, and the die orifice 63 are in the water. The above-mentioned particles are cooled by the water of the interior 11 of the chamber 1. In the lower part of the chamber 1, a through hole as the inflow port 10 is formed in the wall surface 17 of the chamber 1. In the upper part of the chamber 1, a through hole as the outlet 12 is formed in the wall surface 19 of the chamber 1. Water is fed from the inlet 10 into the interior 11 of the chamber 1, the interior 11 is filled with water, and the water in the interior 11 is guided from the outlet 12 to the outside of the chamber 1 and is again fed from the inlet 10 into the interior 11 of the chamber 1.

The control unit 120 will be described with reference to fig. 1. The controller 120 controls the resin pelletizer apparatus main body 110. The control Unit 120 is a computer implemented by a Central Processing Unit (CPU), a Random Access Memory (RAM), a Read Only Memory (ROM), and the like. The control unit 120 includes a determination unit 121, a rotation control unit 123, a storage unit 125, and a stop control unit 127 as functional blocks. These functional blocks will be described later.

The operation panel 130 is a device for inputting the operation of the resin pelletizer apparatus 100. The input includes a command to start the operation of the resin pelletizer device 100, a command to stop the operation, a setting of the rotational speed of the rotary blade 21, and the like.

When it is determined that cavitation has occurred during operation of the resin pelletizer device 100, the reporting unit 140 reports the occurrence of cavitation. The reporting unit 140 is implemented by a display, a speaker, a warning lamp, or the like. When the report unit 140 is a display, an image indicating that cavitation has occurred is displayed. When the reporting unit 140 is a speaker, a sound indicating that cavitation has occurred is output. If the notification unit 140 is a warning lamp, the warning lamp is turned on.

Referring to fig. 1 and 2, a sensor 150 is disposed on a side surface of the die 6. The resin pelletizer apparatus 100 monitors cavitation using a sensor 150. The following description will be made in detail. The rotating blade 21 generates ultrasonic waves while rotating on the die surface 61. Although a predetermined gap is provided between the rotary blade 21 and the die surface 61, it is considered to be a main cause that the rotary blade 21 comes into contact with the die surface 61 by oscillating the rotary shaft 3 rotating the rotary blade 21 in the axial direction while the rotary blade 21 rotates on the die surface 61.

The sensor 150 detects an elastic wave generated during the rotation of the rotary blade 21 on the die surface 61 (an elastic wave generated when the rotary blade 21 rotates on the die surface 61 and the rotary blade 21 comes into contact with the die surface 61). When the ultrasonic wave generated during the rotation of the rotary blade 21 on the die surface 61 is detected as an elastic wave, an Acoustic Emission (AE) sensor is used. When the vibration generated when the rotary blade 21 rotates on the die surface 61 is detected as the elastic wave, a vibration sensor is used. In the present embodiment, an acoustic emission sensor is described as an example of the sensor 150. The output value of the sensor 150 is the intensity of the signal output from the sensor 150, and indicates the magnitude of the ultrasonic wave generated when the rotary blade 21 rotates on the die surface 61.

Fig. 6 is an explanatory diagram illustrating cavitation generated during operation of the resin pelletizer apparatus 100. During operation of the resin pelletizer apparatus 100, the rotary head 2 rotates at a high speed in a state where the inside 11 of the chamber 1 is filled with water, and thereby the rotary blade 21 rotates at a high speed on the die surface 61. The molten resin 600 extruded from the die hole 63 is cut by the rotary blade 21 and molded into pellets.

If the rotation speed of the rotary blade 21 becomes large, cavitation occurs. Reference numeral 700 denotes bubbles generated due to cavitation. As described above, the rotary blade 21 generates ultrasonic waves while rotating on the die surface 61. The ultrasonic waves generated at this time are detected by the sensor 150 (fig. 1). The present inventors have found that as the rotation speed of the rotary blade 21 increases, the output value of the sensor 150 (the intensity of the signal output from the sensor 150) increases, but if cavitation occurs, the output value of the sensor 150 may decrease. This is considered to be because cavitation occurs, the rotary blade 21 oscillates, and the contact pressure between the rotary blade 21 and the die surface 61 is reduced.

The reason why the rotary blade 21 is shaken by the cavitation is not clear. The present inventors presume that the rotating blade 21 is shaken due to the fact that the rotating shaft 3 rotating the rotating blade 21 is inclined by the shock wave generated when the bubble 700 generated by cavitation is extinguished.

Fig. 7 is a graph showing a relationship between the rotation speed of the rotary blade 21 (the rotation speed of the rotary head 2) and the output value of the sensor 150. The horizontal axis represents the rotational speed of the rotary blade 21, and the vertical axis represents the output value of the sensor 150. As the rotation speed of the rotary blade 21 increases, the output value of the sensor 150 repeatedly increases and becomes constant, and the output value of the sensor 150 rapidly decreases when cavitation occurs. By generating the bubble 700 in a large amount, it is known that cavitation has occurred.

Cavitation causes cutting defects. Therefore, referring to fig. 1, the determination unit 121 monitors the output value of the sensor 150, and determines that cavitation has occurred when the output value of the sensor 150 becomes smaller than a predetermined threshold value (for example, the 1 st threshold value Th 1) after the output value of the sensor 150 exceeds the threshold value. Therefore, the resin pelletizer apparatus 100 according to the present embodiment can monitor cavitation.

In the present embodiment, the 1 st threshold Th1 and the 2 nd threshold Th2 smaller than the 1 st threshold Th1 are set as thresholds for monitoring cavitation. This will be explained. Referring to fig. 7, when cavitation occurs, the output value of the sensor 150 decreases as the rotation speed of the rotary blade 21 increases. This is considered to be caused by the fact that the wobbling of the rotary blade 21 becomes large and the contact pressure between the rotary blade 21 and the die surface 61 becomes small. If the wobbling of the rotary blade 21 becomes large, the degree of cutting failure further deteriorates. For example, a plurality of particles connected in a chain shape is produced. This causes the pellets to clog in the interior 11 of the chamber 1 of the resin pelletizer apparatus 100.

The 1 st threshold Th1 and the 2 nd threshold Th2 are determined such that the output value of the sensor 150 is smaller than the 1 st threshold Th1 and equal to or greater than the 2 nd threshold Th2 when cavitation occurs but a large problem does not occur in the resin pelletizer 100 (for example, particles having a beard-like portion are generated due to cutting failure). On the other hand, the 2 nd threshold value Th2 is determined so that the output value of the sensor 150 becomes smaller than the 2 nd threshold value Th2 when cavitation occurs and a large problem occurs in the resin pelletizer device 100 (for example, a plurality of particles connected in a chain form are generated due to cutting failure).

Before the start of the operation of the resin pelletizer apparatus 100, the 1 st threshold Th1 and the 2 nd threshold Th2 are set in advance. The following description will be made in detail. Referring to fig. 1, 2 and 7, in a state where the interior 11 of the chamber 1 is filled with water, the operator operates the operation panel 130 to input a command for setting a threshold value. Thereby, the rotation control unit 123 controls the rotation of the motor 5 to rotate the rotary blade 21. Since the molten resin is not fed into the orifice 63, the molten resin is not extruded from the orifice 63.

The rotation control unit 123 performs control to gradually increase the rotation speed of the rotary blade 21. The determination unit 121 monitors the output value of the sensor 150, and when the output value of the sensor 150 decreases and the amount of decrease exceeds the preset 1 st amount, stores the output value of the sensor 150 at that time in the storage unit 125 as the 1 st threshold Th 1. This completes the setting of the 1 st threshold Th 1.

The determination unit 121 continues to monitor the output value of the sensor 150, and when the output value of the sensor 150 further decreases from the 1 st threshold value Th1 and the decrease amount exceeds the preset 2 nd amount, stores the output value of the sensor 150 at that time in the storage unit 125 as the 2 nd threshold value Th 2. This completes the setting of the 2 nd threshold Th 2.

In the present embodiment, when the amount of decrease in the output value of the sensor 150 exceeds the 1 st amount, the output of the sensor 150 at that time is defined as the 1 st threshold Th 1. However, there is a possibility that cavitation may occur when the decrease amount of the output value of the sensor 150 exceeds the amount smaller than the 1 st amount in the operation of the resin pelletizer device 100 in practice due to an error in the output value of the sensor 150 or the like. Thus, when the amount of decrease in the output value of the sensor 150 exceeds the 1 st amount, the constant multiple of the output value of the sensor 150 at that time may be the 1 st threshold Th 1. The same applies to the 2 nd threshold Th 2.

Next, control of the resin pelletizer 100 using the 1 st threshold Th1 and the 2 nd threshold Th2 will be described. Fig. 8 is a flowchart illustrating it. Referring to fig. 1 and 8, the determination unit 121 monitors the output value of the sensor 150 during the operation of the resin pelletizer device 100 (step S1).

The determination unit 121 determines whether or not the output value of the sensor 150 monitored in step S1 exceeds the 1 st threshold Th1 shown in fig. 7 (step S2). When the determination unit 121 determines that the output value of the sensor 150 monitored in step S1 does not exceed the 1 st threshold Th1 (no in step S2), the determination unit 121 performs the process of step S1. At this time, the reporting unit 140 reports that the output value of the sensor 150 does not exceed the 1 st threshold Th 1. The operator operates the operation panel 130 to adjust the rotation speed of the rotary blade 21.

When the determination unit 121 determines that the output value of the sensor 150 monitored in step S1 exceeds the 1 st threshold Th1 (yes in step S2), the determination unit 121 continues monitoring the output value of the sensor 150 (step S3).

The determination unit 121 determines whether or not the output value of the sensor 150 monitored in step S3 is lower than the 1 st threshold Th1 (step S4). When the determination unit 121 determines that the output value of the sensor 150 monitored in step S3 is equal to or greater than the 1 st threshold Th1 (no in step S4), the determination unit 121 performs the process of step S3.

When the determination unit 121 determines that the output value of the sensor 150 monitored in step S3 is lower than the 1 st threshold value Th1 (yes in step S4), the determination unit 121 determines whether the output value of the sensor 150 monitored in step S3 is lower than the 2 nd threshold value Th2 (step S5).

When the determination unit 121 determines that the output value of the sensor 150 monitored in step S3 is equal to or greater than the 2 nd threshold Th2 (no in step S5), the notification unit 140 notifies that cavitation has occurred while the operation of the resin pelletizer device 100 is continued (step S6). Subsequently, the determination unit 121 performs the process of step S3.

When the determination unit 121 determines that the output value of the sensor 150 monitored in step S3 is lower than the 2 nd threshold Th2 (yes in step S5), the stop control unit 127 stops the operation of the resin pelletizer device 100 (step S7). Thereby, the rotation of the rotary blade 21 is stopped.

As described above, when the determination unit 121 determines that the output value of the sensor 150 is smaller than the 1 st threshold value Th1 (yes in step S2) and equal to or larger than the 2 nd threshold value Th2 (no in step S5), it is considered that a large problem (for example, particles having a beard-like portion due to cutting failure) does not occur in the resin pelletizer device 100, the operation of the resin pelletizer device 100 is continued, and the notification unit 140 notifies the occurrence of cavitation (step S6).

On the other hand, when the determination unit 121 determines that the output value of the sensor 150 is smaller than the 2 nd threshold Th2 (yes in step S5), it is considered that a large problem occurs in the resin pelletizer apparatus 100 (for example, a plurality of pellets connected in a chain form are generated due to a cutting failure), and the stop control unit 127 automatically stops the operation of the resin pelletizer apparatus 100 (step S7).

Next, the upper limit value of the rotation speed of the rotary blade 21 will be described. Cavitation occurs mainly depending on the rotational speed of the rotary blade 21. Cavitation becomes severe as the rotation speed of the rotary blade 21 becomes higher.

Referring to fig. 7, it is understood that cavitation occurs if the rotation speed of the rotary blade 21 exceeds a predetermined value. Therefore, if the upper limit Uv of the rotation speed of the rotary blade 21 is set to a value smaller than the predetermined value, the occurrence of cavitation can be prevented.

The upper limit value Uv is set before the operation of the resin pelletizer apparatus 100 is started. The following description will be made in detail. Referring to fig. 1, 2, and 7, in a state where the interior 11 of the chamber 1 is filled with water, the operator operates the operation panel 130 to input a command for setting the upper limit value Uv. Thereby, the rotation control unit 123 controls the rotation of the motor 5 to rotate the rotary blade 21. Since the molten resin is not fed into the orifice 63, the molten resin is not extruded from the orifice 63.

The rotation control unit 123 performs control to gradually increase the rotation speed of the rotary blade 21. The determination unit 121 monitors the output value of the sensor 150, and when the output value of the sensor 150 decreases and the amount of decrease exceeds the preset 3 rd amount, stores the rotational speed of the rotary blade 21 at that time as the rotational speed at which cavitation occurs, and the rotational speed lower than this as the upper limit Uv in the storage unit 125. Thereby, the setting of the upper limit value Uv is completed.

When the operator operates the resin pelletizer device 100, the operator can select one of the control using the 1 st threshold Th1 and the 2 nd threshold Th2 and the control using the upper limit value Uv. When the operator operates the operation panel 130 and inputs a command for selecting control using the upper limit value Uv, the rotation control unit 123 controls the rotation speed of the rotary blade 21 so as not to exceed the upper limit value Uv stored in the storage unit 125 during the operation of the resin pelletizer device 100. Thereby, occurrence of cavitation can be prevented.

In the present embodiment, two thresholds (the 1 st threshold Th1 and the 2 nd threshold Th 2) are set, but one threshold may be used. This will be described as modification 1 and modification 2 of the present embodiment.

Referring to fig. 1 and 7, the determination unit 121 of modification 1 monitors the output value of the sensor 150, and determines that cavitation has occurred when the output value of the sensor 150 becomes smaller than a predetermined threshold value (for example, threshold value Th1 1). When the determination unit 121 determines that cavitation has occurred, the reporting unit 140 reports the occurrence of cavitation. The 1 st modification example may not include the stop control unit 127.

According to the modification 1, when the determination unit 121 determines that cavitation has occurred, it is possible to report the occurrence of cavitation. Therefore, the operator of the resin pelletizer device 100 can take measures necessary for the occurrence of cavitation (for example, measures to reduce the rotation speed of the rotary blade 21 and measures to stop the operation of the resin pelletizer device 100).

Referring to fig. 1 and 7, the determination unit 121 of modification 2 monitors the output value of the sensor 150, and determines that cavitation has occurred when the output value of the sensor 150 becomes smaller than a predetermined threshold value (for example, the 1 st threshold value Th 1). When the determination unit 121 determines that cavitation has occurred, the stop control unit 127 stops the operation of the resin pelletizer device 100. The modification 2 does not include the report unit 140.

According to the modification 2, when the determination unit 121 determines that cavitation has occurred, the operation of the resin pelletizer device 100 can be automatically stopped.

Description of the reference numerals

6 mould

21 rotating blade

61 die surface

63 die hole

100 resin granulator device

110 resin granulator device body

121 determination unit

123 rotation control part

125 storage part

127 stop control unit

140 report part

150 sensor.

Claims

1. A resin granulator device is characterized by comprising:

the die is provided with a die surface provided with a die hole;

a rotary blade which rotates on the die surface in water to cut the resin extruded from the die hole into pellets in the water;

a sensor for detecting an elastic wave generated by the rotary blade rotating on the die surface;

and a determination unit that monitors an output value of the sensor and determines that cavitation has occurred when the output value of the sensor is smaller than a predetermined threshold from a value larger than the threshold.

2. The resin pelletizer apparatus as set forth in claim 1,

the cavitation control device further includes a reporting unit that reports occurrence of the cavitation when the determination unit determines that the cavitation has occurred.

3. The resin pelletizer apparatus as set forth in claim 1,

the apparatus further includes a stop control unit that stops the operation of the resin pelletizer device when the determination unit determines that the cavitation has occurred.

4. The resin pelletizer apparatus as set forth in claim 1,

the determination unit compares a 1 st threshold value and a 2 nd threshold value smaller than the 1 st threshold value with the output value of the sensor, as the threshold values;

further provided with:

a reporting unit configured to report that the cavitation has occurred when the determination unit determines that the output value of the sensor is smaller than the 1 st threshold and equal to or greater than the 2 nd threshold;

and a stop control unit configured to stop the operation of the resin pelletizer when the determination unit determines that the output value of the sensor is smaller than the 2 nd threshold value.

5. A resin pelletizer apparatus as set forth in any one of claims 1 to 4,

further provided with:

a storage unit that stores in advance an upper limit value of the rotational speed of the rotary blade at which the cavitation does not occur;

and a rotation control unit that controls the rotation speed of the rotary blade to a value not exceeding the upper limit value.

6. A cavitation monitoring method for monitoring cavitation generated in a resin pelletizer apparatus having a die surface with a die hole and a rotary blade for cutting a resin extruded from the die hole into pellets in water by rotating the rotary blade on the die surface in the water,

the disclosed device is characterized by being provided with:

a step 1 of detecting an elastic wave generated by the rotating blade rotating on the die surface;

and a 2 nd step of monitoring the magnitude of the elastic wave detected in the 1 st step, and determining that cavitation has occurred when the magnitude of the elastic wave becomes smaller than a predetermined threshold value from a value larger than the threshold value.